Hydraulic camshaft adjuster with centre locking and adjustable locking play

ABSTRACT

A hydraulic camshaft adjuster-having a stator drivable by the internal combustion engine and having a rotor connectable to a camshaft, wherein the rotor is fixed releasably to the stator via at least one first pin-like locking pin in a rotationally fixed manner in a centre position counter to a first rotational direction. The locking pin is designed for moving into and moving out of a first slotted guide in a first axial direction defined by the rotational axis of the stator and/or of the rotor. A second locking pin can be moved in a second axial direction parallel to the first axial direction but in a different direction, into a second slotted guide, so as to secure the rotor relative to the stator in a centre position counter to a second rotational direction in a different direction to the first rotational direction, and can be moved out of the second slotted guide.

The present invention relates to a hydraulic camshaft adjuster for an internal combustion engine of a motor vehicle, such as a passenger car or a truck, including a stator, which is drivable by the internal combustion engine, such as via a traction mechanism drive, and including a rotor, which is connectable to a camshaft, the rotor being detachably fixed to the stator with the aid of at least one pin-like locking pin in a center position rotatably fixedly counter to a first direction of rotation, the locking pin being designed to retract into and extend out of a first slotted gate in a first axial direction, which is defined by the rotation axis of the stator and/or the rotor.

BACKGROUND

In principle, different systems exist for adjusting the angle of a camshaft of an internal combustion engine. One proven system is based on the vane principle, in which a rotor, which includes radially extending vanes, is situated in a stator and divides chambers in the stator into two opposite working chambers with the aid of the vanes. A pressure medium may be applied to the working chambers using a hydraulic system, when pressure is applied to one working chamber, pressure medium being displaced from the opposite working chamber. The rotor is then adjusted with respect to the stator in one direction of rotation as a function of the pressure application to the working chambers. Since the rotor is connected to the camshaft and the stator to the crankshaft, the rotation angle of the camshaft with respect to the crankshaft also changes. To adjust the rotation angle of the camshaft, either the alternating torques acting upon the camshaft may be used, the pressure medium being displaced from one working chamber into the other working chamber by the alternating torques acting upon the camshaft, this procedure also being referred to as CTA (Camshaft Torque Actuated), or a pressure may be applied to the working chambers by an external pressure medium supply, and the pressure medium may be removed from the opposite working chamber into a pressure medium reservoir, this procedure also being referred to as OPA (Oil Pressure Actuated). The advantage of CTA may be seen in the fact that only a very small externally supplied pressure medium flow is required to adjust the camshaft, while OPA requires a relatively large externally supplied pressure medium flow via a pressure medium pump. The much smaller externally supplied pressure medium flow in the adjustment according to the CTA principle is required exclusively to compensate for the leakage losses of the adjuster, since the pressure medium is displaced from one working chamber into the other working chamber to increase the volume and reduce the size of the working chambers. In addition, much higher adjustment speeds may be reached with the aid of an adjustment according to the CTA principle in the case of high alternating torques acting upon the camshaft than is possible in an adjustment according to the OPA principle. A small pressure medium flow is generally desirable, since the hydraulic system as a whole may thus be provided with a smaller design.

A camshaft adjusting device of this type is known from DE 10 2006 045 005 A1, with the aid of which the angular position of a camshaft with respect to a crankshaft may be adjusted. The camshaft adjusting device described therein includes a hydraulic system having a multi-way valve for applying pressure to multiple working chambers, in which a pressure is variably applied to the working chambers as a function of the position of the valve body in the multi-way valve, and the camshaft is subsequently adjusted with respect to the crankshaft in the different directions of rotation. A two-sidedly acting check valve, including two spring-loaded closure elements, is furthermore provided in the valve body of the multi-way valve, with the aid of which a flow connection between the working chambers is established in certain positions of the valve body. An external pressure application to the working chambers as well as a pressure compensation between the working chambers are possible in certain positions of the valve body, due to the provided check valve in connection with the multi-way valve. However, the disadvantage of an approach of this type is that the check valve itself requires a complex mounting procedure and is itself formed by spring-loaded valve bodies, which may be excited to vibrations under unfavorable conditions.

A pressure medium-actuatable camshaft adjusting device for an internal combustion engine is known from DE 10 2010 022 896 A1, which includes at least two oppositely acting working chambers of a pressure medium pump, a pressure medium reservoir and a housing which includes a multi-way valve and has multiple working chambers, the pressure medium pump and openings assigned to the pressure medium reservoir, through which an inflow and/or outflow of the pressure medium is facilitated, a valve body being used, which blocks or enables the flow of the pressure medium through the openings in the housing with the aid of control edges abutting the housing as a function of the position, and including a check valve device which facilitates the flow of the pressure medium assigned to the valve body from the working chamber into the other working chamber and vice versa. This publication relates to the fact that the valve body includes at least two pressure medium lines, which are each fluidically connectable to one of the working chambers, and the check valve device is formed by spring steel sheets closing the pressure medium lines.

Another switchable device for supplying pressure is also known from DE 10 2010 024 026 A1. In this publication, a switchable device for supplying pressure to at least one consumer of an internal combustion engine is described, in particular for supplying pressure to a camshaft adjuster. It includes a displaceable element situated in a cavity, which is, in particular, a piston, as well as an energy store cooperating with the displaceable element, which is, in particular, a spring element, the displaceable element being displaceable against the force of the energy store from a first end position into a second end position by applying pressure to a reservoir with the aid of a pressure medium. A fault-free operation of the switchable device for supplying pressure is ensured even at low oil pressures or at low engine speeds, in that the energy store is situated in an interior in which underpres sure is set with the aid of a vacuum pump at least during the displacement of the displaceable element from the first end position into the second end position.

However, it is known that, during startup of the internal combustion engine, the problem may occur that insufficient oil pressure is present in the oil circuit of the engine for the purpose of holding the camshaft adjuster in a certain position. The result is that the camshaft adjuster starts to vibrate uncontrollably. Due to the striking of the vanes on the stator, which may also be referred to as the external rotor, noises may furthermore be caused.

It has become known that the aforementioned problem may be resolved by the fact that an axial locking is carried out between the inner rotor and a laterally situated locking cover in the camshaft adjuster. At least one locking action is carried out in one of the “retard” or “advance” end stop positions. The locking play may be adjusted relatively problem-free by correspondingly positioning the inner rotor with respect to the outer rotor before mounting the camshaft adjuster. On the one hand, this play may not be too large, since unwanted noises will otherwise occur; on the other hand, it may also not be too small, since the locking pin, which may also be referred to as the locking rod or locking piston, may otherwise no longer reliably engage or disengage.

However, the locking actions in an “advance” or “retard” end position also have disadvantages, so that it is desirable to be able to carry out a locking action in a center position between “advance” and “retard.” This facilitating center locking differs from the end stop locking in that the camshaft adjuster is locked in a defined angular position between the two “advance” and “retard” end positions, which is advantageous, in particular, when starting the engine. A center locking of this type is known from EP 2 132 417 B1, for example.

It is customary to use V-shaped locking gates for the purpose of making the locking play adjustable, namely by radially shifting the cover. In this approach, however, the locking play is adjustable, but the location of the center locking position itself is also determined by this adjustment. A radial shifting of the cover causes an additional imbalance on the camshaft adjuster, which, however, is to be avoided. Although the locking play, in particular, is to be adjustable, negative effects are, however, to be avoided. The locking play should also be easier to adjust than before.

SUMMARY OF THE INVENTION

An object is therefore to provide an improvement for hydraulic camshaft adjusters, as well as to improve an internal combustion engine as such.

The present invention provides a generic hydraulic camshaft adjuster by the fact that a second locking pin is retractable into a second slotted gate in a second axial direction, which is parallel to the first axial direction but in a different direction, so as to secure the rotor relative to the stator in a center position counter to a second direction of rotation, which is in a different direction from the first direction of rotation, and is extendable from the second slotted gate.

Advantageous specific embodiments are explained in greater detail below.

It is thus advantageous if the rotor is rotatably supported relative to the stator when the first locking pin is not in a form-locked fit with the slotted gate. It is similarly advantageous if the rotor is rotatable relative to the stator in an opposite direction when the second locking pin is not in a form-locked fit with the second slotted gate.

It is furthermore advantageous if the first locking pin and the second locking pin are extendably supported in the rotor. In this way, a form-locked fit may be easily established between the first locking pin and a first slotted gate or between the second locking pin and the second slotted gate. The blocking of a rotary motion of the rotor relative to the stator in a first direction of rotation or in a second direction of rotation may then be efficiently ensured.

One advantageous exemplary embodiment is also characterized in that the first locking pin is extendable from a first front surface of the rotor and the second locking pin is extendable from a second front surface of the rotor, which is situated on the other side of the rotor. In principle, it is, of course, also possible for the locking pin to extend from the stator into a slotted gate of the rotor, although the extension out of the rotor is more advantageous.

The functions of the determination of the center locking position and the adjustment of the locking play may be separated from each other if the first slotted gate is formed in a first cover rotatably securable on the stator, and/or the second slotted gate is formed in a second cover rotatably securable on the stator. It is also possible, in principle, for the slotted gate to be situated in the rotor, if the locking pin is retractably and extendably supported in the cover or in the stator. The slotted gate may also be situated in the stator if the locking pin is retractably and extendably supported in the rotor or the cover.

Mounting is made easier if the stator is situated axially between the first cover and the second cover.

In a hydraulic camshaft adjuster, safety during operation may be optimized as needed if the first or second locking pin is separated from a cartridge by a spring in the axial direction, and if the cartridge, the spring and the locking pin are preferably at least partially situated in a hole oriented in the axial direction, such as a blind hole or a through-hole in the manner of a bore.

To be able to easily mount the cover, it is advantageous if the first cover and/or the second cover is/are fixable on the stator with the aid of at least one screw, preferably if one of the two covers has a threaded section for fastening the screw, the threaded section furthermore preferably being designed as a threaded cover which is rotatably fixedly mountable on the first or second cover, for example in the manner of a ring, or if it is an integral part of the first or second cover. In particular, it is also advantageous if multiple, evenly distributed screws are used, in particular those having a screw head on one end and a threaded section in at least one area of the other end. Of course, it is also possible to use threaded rods without screw heads, rivets and/or bolts.

The ability to shift the covers with respect to each other when the screw is inserted may be ensured if the screw projects through a kidney-shaped or fan-shaped recess, such as an elongated hole, in the first or second cover.

The present invention also relates to an internal combustion engine, which includes a camshaft and a camshaft adjuster controlling the camshaft, which is designed according to the present invention.

In this way, an alternative approach for a center locking position is facilitated, which is independent of the locking play and does not demonstrate any additional imbalance. The locking gates are accommodated in two covers, the covers being rotatable with respect to each other during mounting and ensuring the adjustment of the center locking position and the adjustment of the locking play independently of each other.

The center locking is thus achieved in a hydraulic camshaft adjuster with the aid of two locking gates in the cover, a first locking gate being contained in a front cover and a second locking gate being contained in a rear cover, two locking units including a locking pin, a locking spring and a cartridge being accommodated in the rotor. The locking units are installed in the rotor in an oppositely oriented manner. The first locking pin engages with a first unpressurized locking gate and is pressed back into the rotor by oil pressure coming from a first oil bore or a first oil groove. The second locking pin engages with an unpressurized second locking gate and is pressed back into the rotor by oil pressure coming from a second oil bore or a second oil groove. The oil supply for both locking gates takes place via a separate oil line, separated from the oil supply for the oil chambers.

The camshaft adjuster is thus completely premountable, the cover screws then being not yet tightened, and the front cover being rotatably supported within the elongated holes in the stator and being rotatable into a desired position until the locking play is adjusted, only then this position being mechanically fixed from the outside. A stop in the first locking gate determines the center locking position, since friction torques of the camshaft always press the rotor or the first locking pin in the retard direction, i.e., counterclockwise in the present case. The rear cover is rotatable within the elongated holes formed in the rear cover. The rear cover is initially rotated in such a way that a stop in the second locking gate comes into contact with the locking pin. The locking play may then be 0°. However, play values of 0.6° to 1.2°, preferably 0.8°, are preferably set.

The rear cover is subsequently rotated in the other direction until the desired total locking play is set. The rear cover is also mechanically fixed. The cover screws are tightened only at the end. The threaded cover is tightened on the adjuster and clamps both covers to the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is also explained in greater detail below with the aid of a drawing. A first exemplary embodiment is illustrated in greater detail therein.

FIG. 1 shows a perspective representation of the assembly of a hydraulic camshaft adjuster according to the present invention;

FIG. 2 shows a view of the camshaft adjuster from FIG. 1 from the front, however including a translucent representation of a first, front cover;

FIG. 3 shows the view of the camshaft adjuster in FIGS. 1 and 2 from the rear, including a translucently represented second, rear cover;

FIG. 4 shows a singular representation of the rotor, including two locking devices situated therein and extendable in a different direction; and

FIG. 5 shows a view of this camshaft adjuster in FIGS. 1 through 3 from the rear, i.e., in a representation as in FIG. 3, however, unlike in this figure, including only one threaded cover.

DETAILED DESCRIPTION

The figures are only schematic and are used only for the sake of understanding the present invention. Identical elements are provided with identical reference numerals.

FIG. 1 shows a first specific embodiment of a hydraulic camshaft adjuster 1. A camshaft adjuster 1 of this type uses a pressure provided by a fluid. A fluid of this type may be oil and is conducted into different pressure chambers between a stator 2 and a rotor 3.

In FIG. 2, the pressure chambers are provided with reference numeral 4. Pressure chambers 4 are divided into a first pressure space and a second pressure space 7 with the aid of vanes 5, which are fixedly situated in rotor 3. In both FIGS. 1 and 2, it is apparent that rotor 3 is radially situated within stator 2. A first, front cover 9 on the front side of rotor 3 is fastened to stator 2, with the aid of preferably five screws 8, which may also be referred to as cover screws.

Rotor 3 is connectable or connected to a camshaft. Stator 2 has teeth 10 on its outside, which ensure a connection to a crankshaft of an internal combustion engine via a traction mechanism drive.

In FIG. 2, it is apparent that a first slotted gate 11 is present in first cover 9. This first slotted gate 11 may also be referred to as a locking gate and is used to fix a position of rotor 3 relative to stator 2, since first cover 9 is rotatably fixedly connected to stator 2 with the aid of screws 8.

A first pin-like locking pin 12, which could also be referred to as a locking rod or locking piston, is extendably supported in rotor 3 in a first axial direction, so that it achieves a form fit, abutting on one side, with first slotted gate 11 when it is extended. The first axial direction is oriented in parallel to a rotation axis 13.

First locking pin 12 is part of a first locking device, which additionally also has a first locking spring 14, as well as a first cartridge 15, locking spring 14 being designed as a spiral spring and being situated upright between first locking pin 12 and first cartridge 15 and being in contact with them both. This is illustrated, for example, in FIG. 4.

It is also apparent that a second locking pin 16 exists, which, together with a second locking spring 17 and a second cartridge 18, is part of a second locking device. The two locking devices are continuously provided with the same design but are inserted in a different direction into rotor 3, so that first locking pin 12 is extendable from a first front side 19 of rotor 3, and second locking pin 16 is extendable from a second front side 20 of rotor 3. First front side 19 may also be referred to as the first front surface, just as second front side 20 may also be referred to as the second front surface. First cartridge 15 and second cartridge 18 are situated within rotor 3, as are first locking spring 14 and second locking spring 17.

In principle, the two locking devices are situated in two different through-holes 21. However, the two locking devices may also be situated in a single through-hole 21. Only two locking devices are provided here, which, however, does not prevent multiple locking devices, for example four or six locking devices, from being present. However, it is advantageous if this is limited to two locking devices.

To return to FIG. 2, it should be further noted that hydraulic fluid, such as oil, is conductable via a first oil bore 22 and a first oil groove 23 from an innermost radial area in first slotted gate 11, which may be referred to as a locking gate, for the purpose of forcing first locking pin 12 back into rotor 3.

To ensure the venting function, through-holes 21 are provided with radially inwardly running venting grooves 24.

It is also advantageous if screws 8 project into stator 2 through through-holes designed as elongated holes 25. Elongated holes are also provided in a second cover 26, which, however, are provided with reference numeral 27. Screws 8 also project through these elongated holes 27. Either the one elongated holes 25 or the other elongated holes 27 may be used.

A second slotted gate 28, which engages with second locking pin 16, is situated in second cover 26. In a manner similar to first locking pin 12, oil may also be supplied to second locking pin 16 via a second oil bore 29 and a second oil groove 30.

While first locking pin 12 establishes a form-locked fit with first slotted gate 11 upon reaching the center locking position, second locking pin 16 simultaneously establishes a form-locked fit with second slotted gate 28, the form-locked surfaces or stops being situated opposite each other. The form-locked fit between first locking pin 12 and first slotted guide 11 prevents the rotation of the rotor relative to the stator in one direction of rotation, while the form-locked fit between second locking pin 16 and second slotted gate 28 prevents the rotation in the other direction. The two directions of rotation are thus opposed to each other, once in the “retard” direction and once in the “advance” direction.

While the screws, as is apparent in FIG. 1, for example, have screw heads 31 on the one side, they have only a threaded area 32 on the other side, which establishes a pivot fit with a threaded section 33 of second cover 26.

In the exemplary embodiment in FIG. 5, threaded section 33 is designed as a separate component from second cover 26, namely as an independent threaded cover 34. Threaded cover 34 is in the shape of a ring.

Threaded cover 34 is rotatably immovably connected to second cover 26.

LIST OF REFERENCE NUMERALS

-   1 Camshaft adjuster -   2 Stator -   3 Rotor -   4 Pressure chamber -   5 Vane -   6 First pressure space -   7 Second pressure space -   8 Screw -   9 First cover -   10 Tooth -   11 First slotted gate -   12 First locking pin -   13 Rotation axis -   14 First locking spring -   15 First cartridge -   16 Second locking pin -   17 Second locking spring -   18 Second cartridge -   19 First front side -   20 Second front side -   21 Through-hole -   22 First oil bore -   23 First oil groove -   24 Venting groove -   25 Elongated hole -   26 Second cover -   27 Elongated hole -   28 Second slotted gate -   29 Second oil bore -   30 Second oil groove -   31 Screw head -   32 Threaded area -   33 Threaded section -   34 Threaded cover 

What is claimed is: 1-9. (canceled)
 10. A hydraulic camshaft adjuster comprising: a stator; and a rotor connectable to a camshaft, the rotor being detachably fixed to the stator with the aid of at least one first locking pin in a center position rotatably fixedly counter to a first direction of rotation, the first locking pin being designed to retract into and extend out of a slotted gate in a first axial direction defined by a rotation axis of the stator or the rotor, a second locking pin being retractable into a second slotted gate in a second axial direction parallel to the first axial direction but in a different direction, so as to secure the rotor relative to the stator in the center position counter to a second direction of rotation in a different direction from the first direction of rotation, and is extendable out of the second slotted gate.
 11. The camshaft adjuster as recited in claim 10 wherein the rotor is rotatably supported relative to the stator in at least the first direction of rotation when the first locking pin is not in a form-locked fit with the first slotted gate, or the rotor is rotatably supported relative to the stator in at least the second direction of rotation when the second locking pin is not in a form-locked fit with the second slotted gate.
 12. The camshaft adjuster as recited in claim 10 wherein the first locking pin and the second locking pin are extendably supported in the rotor.
 13. The camshaft adjuster as recited in claim 10 wherein the first locking pin is extendable from a first front surface of the rotor, and the second locking pin is extendable from a second front surface of the rotor situated on an other side of the rotor.
 14. The camshaft adjuster as recited in claim 10 wherein the first slotted gate is formed in a rotatably securable first cover on the stator, or the second slotted gate is formed in a rotatably securable second cover on the stator.
 15. The camshaft adjuster as recited in claim 14 wherein the stator is situated axially between the first cover and the second cover.
 16. The camshaft adjuster as recited in claim 10 wherein the first or second locking pin is separated from a cartridge by a spring, and the cartridge, the spring and the locking pin are at least partially situated in a hole oriented in the axial direction.
 17. The camshaft adjuster as recited in claim 16 wherein the hole is a blind hole or a through-hole.
 18. The camshaft adjuster as recited in claim 14 wherein the first cover or the second cover is fixable to the stator with the aid of at least one screw.
 19. The camshaft adjuster as recited in claim 18 wherein one of the first and second covers has a threaded section for fastening the screw.
 20. The camshaft adjuster as recited in claim 19 wherein the threaded section is designed as a threaded cover rotatably fixedly mountable on the first or second cover.
 21. The camshaft adjuster as recited in claim 20 wherein the threaded cover is a ring or an integral part of the first or second cover.
 22. The camshaft adjuster as recited in claim 18 wherein the screw projects through a kidney-shaped or fan-shaped recess.
 23. The camshaft adjuster as recited in claim 22 wherein the recess is an elongated hole in the first or second cover. 